Effect of substrate preparation and deposition conditions on the preferred orientation of TiN coatings deposited by RF reactive sputtering

Titanium nitride (TiN) coatings have been deposited by RF reactive magnetron sputtering of a titanium target, in an atmosphere of argon and nitrogen. The coatings were deposited using different deposition conditions of gas composition, total pressure and indicated substrate temperature, on to titanium substrates that had received different preparation treatments. The structure of the coatings was examined as a function of deposition conditions by X-ray diffraction, and the crystallographic orientation was determined by use of a texture coefficient. The coatings on ground titanium substrates developed a strong (111) orientation from the earliest stages of growth, although the degree of orientation was dependent on deposition conditions. Although gas composition had no effect on film orientation, the intensity of the (111) orientation diminished with increasing pressure, as well as with increasing substrate temperature. On polished titanium substrates, the initial texture was (220), but this changed to (111) orientation with increasing coating thickness. The results are discussed in terms of thermodynamically stable orientations and the kinetics of coating development as a function of atomic matching of the coating and substrate.